GROWTH AND MANAGEMENT OF PmON IN NEW MEXICO 

 By He^rman H. Chapman and C. E. Behre 



But little scientific data is at hand to show the growth and possibili- 

 ties of management of pifion (Pinus cdulis) in the Southwest. C. E. 

 Behre recently collected growth data on 14 trees on the Santa Fe 

 National Forest, near Glorieta, to determine approximately the period 

 required to produce a mining prop 6 to 8 feet long and 4 inches at top. 



The trees grew in a typical piiion site on the top and south slope of 

 a dry, rocky ridge with coarse, gravelly, dry, and shallow soil, under- 

 laid with sandstone and no ground cover or underbrush, at an altitude 

 of 7,000 feet. As the trees analyzed had been cut for props, the 

 measurements were confined to the taking of stump height, diameter 

 inside bark, and age of stump and the length of prop or section, with 

 its age and diameter inside bark at the top end. The total height of the 

 tree was also obtained by measuring the length of unused top. 



Because of the exceedingly slow growth of the pifion and the difficulty 

 of exact counts of the rings, even with a glass, no attempt was made to 

 measure the rings by decades ; but a total count sufficed, and this was 

 taken as the average of the results of two counts, unless differences 

 greater than one decade were shown. This figure was then reduced to 

 terms of numbers of years required to grow one inch at stump and 

 at top of prop. 



Height growth between stump and top cut was obtained by dividing 

 length by difference in age of the stump and top sections and from total 

 height on total age. The period required to reach stump height was 

 obtained by analyzing a few seedlings. 



Average taper was found to be i inch for 7 feet in lengtii, for the 

 merchantable bole. From curves of. diameter growth at stump, and 

 this figure for taper, the conclusion was reached that a tree measuring 

 4.86 inches on the stump would give a prop 4 inches at top and 6 feet 

 long at the age of 150 years, 15 years of which are re(|uired for the 

 seedling to grow to stump height of 10 inches, and that an 8-foot prop 

 4 inches at top would require 155 years. Twelve feet of merchantable 

 length, or two 6-foot pro])s, require 170 years total age. Thus a rota- 

 tion of 170 years would double the yield of props as against 150 years, 

 provided all trees grew straight enough to yield tlic r(.'(|uire(l diiiicu- 

 sions, which is not usually the case. 



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